1. Field of the Invention
This invention relates to valves having a disc extending across the bore of the valve housing for preventing the flow of fluid through a pipe string in a well bore until the disc is ruptured.
2. Background Information
Valves of this type have utility whenever the valve, once opened, need not be closed again. For example, such valves have been used in drill stem test tools to keep the tubing above the test tools isolated from the fluid in the well bore until such time as it is desired to expose the formation being tested to the pressure in the tubing. They can be used to keep tubing pressure from acting on a pressure operated firing head for perforating guns until everything is ready for the guns to fire.
In the past, frangible discs, usually made of cast iron, have been used for these purposes. The discs were broken by dropping a go-devil or striking the disc in some manner with sufficient force to cause the hard, brittle, material, from which it was made to shatter. As a result, there were pieces of the disc in the pipe string to be carried along with the flowing fluid and plug down hole chokes and surface equipment.